Ballast water refers to sea water that is charged into a ballast tank of a vessel to maintain balance of the vessel when the vessel sails without cargo.
As marine transportation rates have gradually increased along with an increase in international trade, the number of vessels used has increased, and the vessels used are becoming larger. As a result, the amount of ballast water used in vessels has greatly increased. As the amount of ballast water used in vessels is increased, occurrence of damage to indigenous ocean ecosystems attributable to the introduction of foreign marine creature species is also increased. To solve such international environmental issues, in 2004, the IMO (International Maritime Organization) established ‘International Convention for the Control and Management for ships’ Ballast Water and Sediments'. Since 2009, ballast water treatment apparatuses have been obligatorily installed in newly constructed vessels. Of apparatuses for treating ballast water, ultraviolet ballast water treatment apparatuses that sterilize ballast water using ultraviolet rays are widely used.
In a conventional ultraviolet ballast water treatment apparatus, as shown in FIGS. 1, 2, 3, and 10, a single wiper part 10044 is provided on an inner circumferential surface of an annular wiper body 10042. When the wiper body 10042 is moved forward and backward, the wiper part 10044 removes foreign substances adhering to the surface of the ultraviolet lamp 1002. However, in the conventional case where the single wiper part 10044 is installed in the wiper body 10042, when the wiper part 10044 is moved forward along with the wiper body 10042, the wiper part 10044 is bent rearward. Reversely, when the wiper part 10044 is moved backward, it is bent forward. Such continuous friction of the wiper part 10044 easily deforms or wears the wiper part 10044, thus reducing the replacement cycle therefor. Consequently, the operation of the ultraviolet ballast water treatment apparatus must also be frequently interrupted. Moreover, if the wiper part 10044 is repeatedly bent forward and rearward interlocking with the forward and backward movement of the wiper body 10042 while removing foreign substances from the ultraviolet lamp 1002, the edge of the wiper part 10044 becomes excessively softened, whereby the force of removing foreign substances is reduced, and the efficiency of removal of foreign substances is thus reduced.